Effects of Starting Body Weight, Body Condition, and Age on Gain of Cattle Grazing Native Grass11Kansas Agric. Exp. Stn. Contribution No. 00-444-E.

Abstract

<h2>Abstract</h2> In 29 trials over 10 yr, 6614 head of cattle (heifers: 11 trials, 2862 head; steers: 18 trials, 3752 head) were used to determine the effect of starting BW on gain while grazing native grass pastures. The heifers grazed for an average of 81 d (range, 70 to 93 d), and steers grazed for an average of 86 d (range, 75 to 99 d) from April to July. Average stocking rate was one animal per 0.81ha (0.65 animal unit month/0.27 ha). The cattle were sorted by starting BW into five groups as follows: below 181kg, 182 to 227kg, 228 to 272kg, 273 to 318kg, and above 319kg. In three additional trials, 602 yearling heifers were sorted by starting BW, as described previously, and assigned a body condition score from 1 (thinnest) to 5 (fattest). A separate grazing trial was conducted in which 158 yearling steers were compared with 103 steer calves. The yearlings were springborn and wintered on wheat pasture; the calves were fall-born. Heifers between 182 and 227kg gained more BW (P<0.08) than did heifers that weighed more than 273kg. Steers with starting BW between 182 and 227kg and 228 to 272kg gained substantially more (P<0.01) than did steers in other BW groups. Steers gained faster than heifers (1.05 vs 0.86kg/d; P<0.001). As heifers became fatter, gain declined in all weight groups. Fall-born steer calves (202kg) gained slower (1.11 vs 1.22kg/d; P<0.01) than did spring-born yearling steers (267kg). These data indicate that maximum BW gain is achieved when starting BW for stocker cattle grazing native grass for less than 100 d is between 182 and 227kg for heifers and between 182 and 272kg for steers. Yearling steers gained faster than calves. In conclusion, sex, age, and starting BW of cattle affect their gains while grazing native grass pastures. The optimum weight for best pasture gain may vary by forage type and quality, but there is an ideal weight range for stocker cattle used for grazing.